The long-range goal of this work is to obtain a better understanding of molecular evolution as it applies to multi-subunit enzymes. Emphasis will be placed on the structural and catalytic relationship of two closely-related aminoaldehyde dehydrogenases from a Pseudomonas species. The proposal takes advantage of the fairly recent evolutionary divergence of these two enzymes in order to experimentally verify the current concepts of protein evolution, and to determine the effects of subunit hybridization of these functionally distinct enzymes upon the structure and function of the resultant hybrides. Further studies will also be conducted on the more-distantly related succinic semialdehyde dehydrogenase from this organism and the hybrids which it forms with 4-aminobutanal dehydrogenase subunits. Effects of hybridization upon structure, catalysis and immunogenic determinants will be studies. The possible evolutionary relationship of the NAD and NADP-specific succinic semialdhyde dehydrogenases will also be investigated.